Recently, attention has been focused on optical fibers mainly in communication fields. Particularly in the IT (Information Technology) field, a communication technique of employing the optical fibers is necessary to provide a high speed Internet network.
The optical fiber has features: (1) low loss, (2) high band, (3) small diameter and light weight, (4) non-induction, (5) resource saving and the like. A communication system which employs the optical fibers having these features can considerably decrease the number of relays as compared with a communication system which employs conventional metallic cables, can be easily constructed and maintained, and can improve its economical development and reliability.
Further, since the optical fiber can transmit not only light having a single wavelength but also light having many different wavelengths simultaneously, i.e., only one optical fiber can provide multiple transmission of light having many different wavelengths, it is possible to realize a large capacity of a transmission path capable of dealing with diversified purposes and deal with picture service and the like.
Therefore, in the field of the network communication such as the Internet communication, it is proposed that optical transmission using optical fibers apply not only to the communication of a basic network but also to the communication between the basic network and a terminal device (a personal computer, a mobile, a game machine or the like), and the communication between the terminal devices.
When the optical communication is used for the communication between the basic network and the terminal device, an IC which processes information (signals) in the terminal device operates by means of an electric signal, and the terminal device is, therefore, required to include a unit that converts an optical signal into an electric signal or vice versa such as an optical-to-electric converter or an electric-to-optical converter (which device will be also referred to as “optical/electric converter” hereinafter).
For this reason, the conventional terminal device is equipped with the following: a package substrate, on which an IC chip is mounted; an optical component such as a light receiving element or a light emitting element and the like which process optical signals; an optical waveguide which transmits an optical signal transmitted from the outside through an optical fiber or the like to an optical/electric converter and transmits an optical signal transmitted from the optical/electric converter to the optical fiber or the like; a multilayered printed circuit board which transmits an electric signal through a solder bump and the like; and electric wirings and the optical waveguide which are connected to these elements, thereby performing signal transmission and signal process.